A laterally-fused N-heterocyclic carbene framework from polysubstituted aminoimidazo[5,1-b]oxazol-6-ium salts

• Andrew D. Gillie,
• Matthew G. Wakeling,
• Bethan L. Greene,
• Louise Male and
• Paul W. Davies

Beilstein J. Org. Chem. 2024, 20, 621–627, doi:10.3762/bjoc.20.54

• , has been developed and used to access monoligated Au(I), Cu(I) and Ir(I) complexes. The NHC precursors, polysubstituted 3-aminoimidazo[5,1-b]oxazol-6-ium salts are readily prepared in an efficient two-step sequence from ynamides using a newly developed nitrenoid reagent 4. The resulting AImOxAu(I

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• ][42][43][44][45][46], azulenes and their homologous compounds [32][47][48][49][50][51][52][53][54][55][56][57][58], boron dipyrromethenes (BODIPYs) [41][59][60][61], porphyrins [62][63][64], chlorophylls [65][66], triazenes [67][68], ynamides [69][70][71], arylynamines [72], indoles [73], and γ

• to the presence of competitive processes, such as energy or electron transfer. Trolez et al. investigated the photoluminescence properties of various fluorophore-containing TCBDs synthesized via reactions between ynamides and TCNE [139]. The study revealed that numerous fluorenyl derivatives and

N-Sulfenylsuccinimide/phthalimide: an alternative sulfenylating reagent in organic transformations

• Fatemeh Doraghi,
• Seyedeh Pegah Aledavoud,
• Mehdi Ghanbarlou,
• Bagher Larijani and
• Mohammad Mahdavi

Beilstein J. Org. Chem. 2023, 19, 1471–1502, doi:10.3762/bjoc.19.106

• . Organocatalytic sulfenylation for synthesis a diheteroatom-bearing tetrasubstituted carbon centre. Thiolative cyclization of yne-ynamides. Synthesis of alkynyl and acyl disulfides from reaction of thiols with N-alkynylthio phthalimides. Oxysulfenylation of alkenes with 1-(arylthio)pyrrolidine-2,5-diones and

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• corresponds to the observed major isomer product (Figure 15). In a related transformation, Hong realized the exclusively α-selective hydroacylation of ynones, ynoates, and ynamides via photoredox nickel catalysis. Thus, the combination of nickel and iridium catalysts efficiently catalyzed the regioselective α

• reaction, TIPS-protected ynones, ynoates, and ynamides smoothly transformed into the corresponding trisubstituted alkenes 63 in high regio- and stereoselectivities. A possible mechanism was proposed similar to the one shown in Figure 15 to account for the observed high regioselectivity. Allylation The

On the application of 3d metals for C–H activation toward bioactive compounds: The key step for the synthesis of silver bullets

• Renato L. Carvalho,
• Amanda S. de Miranda,
• Mateus P. Nunes,
• Roberto S. Gomes,
• Guilherme A. M. Jardim and
• Eufrânio N. da Silva Júnior

Beilstein J. Org. Chem. 2021, 17, 1849–1938, doi:10.3762/bjoc.17.126

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• cycloisomerization/Pictet–Spengler cyclization of 2-(4-aminobut-1-yn-1-yl)aniline [16], the Ru and Rh-catalyzed [2 + 2 + 2] cycloadditions of yne-ynamides [17], and the Pd-catalyzed tandem coupling-cyclization [18] are significant works in the area (Scheme 1). However, the use of toxic and expensive metal catalysts

When metal-catalyzed C–H functionalization meets visible-light photocatalysis

• Lucas Guillemard and
• Joanna Wencel-Delord

Beilstein J. Org. Chem. 2020, 16, 1754–1804, doi:10.3762/bjoc.16.147

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• aryl radical on ynamides or cyanamides, followed by a final cyclization. Using similar reaction conditions as those used for the Meerwein arylation, the three alkaloids were synthesized in good to excellent yield in a straightforward manner. In 2017, Fu, Peters, and co-workers reported the copper

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• Analysis, Qufu 273165, P. R. China 10.3762/bjoc.15.255 Abstract A formal [3 + 2] cycloaddition between ynamides and unprotected isoxazol-5-amines has been developed in the presence of catalytic AgNTf2 in an open flask. By the protocol, a variety of functionalized 5-amino-1H-pyrrole-3-carboxamide

• employment of isoxazole nucleophiles in gold-catalyzed formal [3 + 2] cycloaddition reaction of ynamides [31][32], and zinc-catalyzed the reaction of ynol ethers [33], giving the respective multi-substituted pyrrole derivatives efficiently (Scheme 2a) [34][35]. The reaction proceeds via an α-imino gold

• carbene pathway presumed by mechanistic studies and theoretical calculations. Following our ongoing interest in the alkyne chemistry [36][37][38], we recently envisaged that the reaction of ynamides with isoxazoles could proceed under silver catalysis conditions, involving the generation of α-imino silver

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• required a high temperature set by classic heating or microwave irradiation. Using cholic acid as carboxylic acid component, Cui and co-workers [37] developed a novel MCR resembling the Ugi-4CR, but relying on the reactivity of ynamides as surrogates of the isocyanide component. Ynamides are alkynes with a

• of a Lewis acid like BF3·Et2O for a suitable activation of the imine. Based on the same idea of exploiting the reactivity of ynamides, Cui’s group developed a 3CR wherein an o-hydroxy-benzhydryl alcohol was used in place of the aldehyde or imine components upon reaction with ynamide and a carboxylic

Recent advances in copper-catalyzed C–H bond amidation

• Jie-Ping Wan and
• Yanfeng Jing

Beilstein J. Org. Chem. 2015, 11, 2209–2222, doi:10.3762/bjoc.11.240

• catalytic protocol was later developed by Mizuno et al. [74] for the amidation of terminal alkynes using lactam, sulfonamide or cyclic carbamates. The application of Cu(OH)2 as heterogeneous catalyst allowed the synthesis of ynamides 77 with moderate to excellent yield under air (Scheme 20). A latest work

• on this area from Truong et al. [75] showed that the heterogeneous and recyclable Cu2(BDC)2(BPY) catalyst (BDC = benzene- 1,4-dicarboxylate; BPY = 4,4′-bipyridine) could catalyze this kind of amidation reaction with excellent selectivity to provide ynamides. Another point was that the C–H bond could

Why base-catalyzed isomerization of N-propargyl amides yields mostly allenamides rather than ynamides

• Armando Navarro-Vázquez

Beilstein J. Org. Chem. 2015, 11, 1441–1446, doi:10.3762/bjoc.11.156

• furnish N-allenyl compounds (allenamides/allencarbamates) or further evolve to N-alkynyl compounds (ynamides or yncarbamates). The particular fate of this reaction varies from experiment to experiment and there is no clear rule for predicting the reaction outcome for a particular structure. With the

• predict the experimentally observed behavior for several examples from the literature. Keywords: allenamide; DFT; isomerization; ynamide; Introduction Allenamides [1][2] and ynamides [3][4][5] have become useful functional groups for organic chemistry synthesis in the last years. Reduced electron pair

• Hsung and coworkers, “…This poses an interesting fundamental question as to why the thermodynamically more stable ynamide … was not found if these isomerizations involved an equilibration mechanism…” [2]. The available experimental data strongly suggest that allenamides do not always convert to ynamides

Synthesis of 3,4-dihydro-1,8-naphthyridin-2(1H)-ones via microwave-activated inverse electron-demand Diels–Alder reactions

• Salah Fadel,
• Youssef Hajbi,
• Mostafa Khouili,
• Said Lazar,
• Franck Suzenet and
• Gérald Guillaumet

Beilstein J. Org. Chem. 2014, 10, 282–286, doi:10.3762/bjoc.10.24

• Paudler [34][50], i.e., the phenylglyoxal was condensed with the S-methylthiosemicarbazide followed by an oxidation reaction with MCPBA. Synthesis of N-substituted pent-4-ynamides N-Alkyl or N-aryl-pent-4-ynamides were prepared by amide coupling reactions between pent-4-ynoic acid and various amines in

• THF in the presence of EDCI and DMAP. The corresponding amides 2–5 were obtained in excellent yields (Scheme 2). The results are shown in Table 1. Preparation of N-substituted N-triazinylpent-4-ynamides The nucleophilic substitution of the methylsulfonyl leaving group from 1 by the lithium salt of

• ynamides 2–5 [22][23][24][53] afforded triazinylpent-4-ynamides 6–9 in moderate to good yields (Scheme 3, Table 2). Intramolecular inverse electron-demand Diels–Alder reactions With the tethered triazines 6–9 in hand, we were able to study the cycloaddition reaction under microwave heating following the

Gold-catalyzed intermolecular coupling of sulfonylacetylene with allyl ethers: [3,3]- and [1,3]-rearrangements

• Jungho Jun,
• Hyu-Suk Yeom,
• Jun-Hyun An and
• Seunghoon Shin

Beilstein J. Org. Chem. 2013, 9, 1724–1729, doi:10.3762/bjoc.9.198

• [4][5]. Recently, strategies capitalizing upon donor- or acceptor-polarized alkynes have been introduced, perhaps to enhance the charge interaction and thus to facilitate the intermolecular reactivity (Figure 1). For example, Liu and co-workers have utilized ynamides for intermolecular [4 + 2] and [2

Regio- and stereoselective carbometallation reactions of N-alkynylamides and sulfonamides

• Yury Minko,
• Morgane Pasco,
• Helena Chechik and
• Ilan Marek

Beilstein J. Org. Chem. 2013, 9, 526–532, doi:10.3762/bjoc.9.57

• carbocupration reactions of heterosubstituted alkynes allow the regio- and stereoselective formation of vinyl organometallic species. N-Alkynylamides (ynamides) are particularly useful substrates for the highly regioselective carbocupration reaction, as they lead to the stereodefined formation of vinylcopper

• : carbometallation; enamides; organocopper; regiochemistry; ynamides; Introduction Due to a strong differentiation of electron density on the two sp-hybridized carbon atoms, N-alkynylamides (ynamides) have become attractive substrates involved in many synthetically useful transformations [1][2][3][4]. The

• ynamides to be of easy access to the whole synthetic community [8][9][10][11][12][13][14]. Similarly, enamides are another important class of substrates involved in numerous applications in organic synthesis [5][15]. As one of the most straightforward and well-developed methods to generate polysubstituted

Recent advances in transition-metal-catalyzed intermolecular carbomagnesiation and carbozincation

• Kei Murakami and
• Hideki Yorimitsu

Beilstein J. Org. Chem. 2013, 9, 278–302, doi:10.3762/bjoc.9.34

• directing group to control the regioselectivity to afford 2E (Scheme 13, path B) [25][74][75][76]. In 2009, Lam reported the rhodium-catalyzed carbozincation of ynamides. The reaction smoothly proceeded under mild conditions to provide the corresponding intermediate 2i regioselectively (Scheme 14) [77][78

• ]. A wide variety of ynamides and organozinc reagents could be used for the reaction (Table 2). Yorimitsu and Oshima reported an interesting transformation of ynamides to nitriles by a carbomagnesiation/aza-Claisen rearrangement sequence (Scheme 15) [79][80]. Carbomagnesiation and carbozincation of

• -bearing hydroxy group. Arylmagnesiation of (2-pyridyl)silyl-substituted alkynes. Synthesis of tamoxifen from 2g. Controlling regioselectivity of carbocupration by attaching directing groups. Rhodium-catalyzed carbozincation of ynamides. Synthesis of 4-pentenenitriles through carbometalation followed by

Intramolecular carbolithiation of N-allyl-ynamides: an efficient entry to 1,4-dihydropyridines and pyridines – application to a formal synthesis of sarizotan

• Wafa Gati,
• Mohamed M. Rammah,
• Mohamed B. Rammah and
• Gwilherm Evano

Beilstein J. Org. Chem. 2012, 8, 2214–2222, doi:10.3762/bjoc.8.250

• 10.3762/bjoc.8.250 Abstract We have developed a general synthesis of polysubstituted 1,4-dihydropyridines and pyridines based on a highly regioselective lithiation/6-endo-dig intramolecular carbolithiation from readily available N-allyl-ynamides. This reaction, which has been successfully applied to the

• formal synthesis of the anti-dyskinesia agent sarizotan, further extends the use of ynamides in organic synthesis and further demonstrates the synthetic efficiency of carbometallation reactions. Keywords: carbolithiation; carbometallation; dihydropyridines; organolithium reagents; pyridines; sarizotan

• ; ynamides; Introduction Since the discovery of the carbometallation reaction by Ziegler and Bähr in 1928 [1], this reaction has evolved as a most powerful tool to construct carbon–carbon bonds. An ever increasing number of organometallic species have been shown over the years to be suitable reagents for

High chemoselectivity in the phenol synthesis

• Matthias Rudolph,
• Melissa Q. McCreery,
• Wolfgang Frey and
• A. Stephen K. Hashmi

Beilstein J. Org. Chem. 2011, 7, 794–801, doi:10.3762/bjoc.7.90

• ][24][25]. Moreover, interesting new pathways were opened when ynamides and alkynyl ether substrates were employed: Here A is also a possible intermediate along these pathways [25]. Since direct experimental evidence existed only for C and D, we intended to intercept the postulated carbenoid

Recent advances in carbocupration of α-heterosubstituted alkynes

• Ahmad Basheer and
• Ilan Marek

Beilstein J. Org. Chem. 2010, 6, No. 77, doi:10.3762/bjoc.6.77

• change the stereochemical outcome of the reaction. Representative examples are given in this mini-review. Keywords: alkynes; carbocupration; enamides; regioselectivity; stereoselectivity; syn-addition; vinylcopper; ynamides; ynol ether; Review The addition of a carbon-metal bond of an organometallic

• the charge distribution in the alkyne (electron donating nitrogen atom induces polarization) [11][12][13]. To obtain the opposite regioisomer for nitrogen-substituted alkynes (linear isomer), it is essential to overcome the effect of the electron-donating heteroatom. Therefore, ynamides 17

• adduct 29. However, the reaction was not completely stereoselective (Scheme 13) [25]. Although not a copper-mediated transformation, the rhodium-catalyzed carbozincation of ynamides should be noted since the regioselectivities were, in general, high (>19:1), though in some cases somewhat diminished with